Process for dyeing polyvinyl chloride fibers



Oct. 13, 1970 c. MAZZOLINI ETAL ,5

PROCESS FOR DYEING POLYVINYL CHLORIDE FIBERS Filed April 21, 19s? I I IINVENTOR! ammo Ima -1M;

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United States Patent 3,533,729 PROCESS FOR DYEING POLYVINYL CHLORIDEFIBERS Corrado Mazzolini, Sergio L0 Monaco, and Giorgio Cazzaro, Mestre,Venezia, Italy, assignors to A.C.S.A. Ap-

plicazioni Chimiche S.p.A., Milan, Italy Filed Apr. 21, 1967, Ser. No.632,715 Claims priority, appgaafildrfilltaly, May 6, 1966,

Int. Cl. D06p 3/00 US. Cl. 8--162 7 (Zlaims ABSTRACT OF THE DISCLOSUREBACKGROUND or THE INVENTION The present invention relates to a processfor dyeing continuously, uniformly and deeply, shaped articles such asfibers, filaments, films, etc. obtained from vinyl chloride and, moreparticularly, it relates to the dyeing of fibers or other shapedarticles of polyvinyl chloride having a high syndiotactic index.

The term polyvinyl chloride with a high syndiotactic index, as used inthe present specification and in the claims, comprises both the vinylchloride homopolymers and its copolymers or mixtures of polymers with atleast 85% by weight of vinyl chloride, having a syndiotactic indexhigher than 1.8 (the syndiotactic index being defined by the absorptionratio at the LR. bands D 635 and D 692 cmf as described by Fordham,Burleigh, and Sturm, J.A.C.S., vol. XLI, pages 7382, 1959).

The polyvinyl chloride with a high syndiotactic index may be transferredinto fibers by dry or wet spinning and the fibers thus obtained presentexcellent chemical and physical properties and an excellent stability toheat and to dry cleaning.

On the contrary, their dyeability is not so good, since the afiinity ofthese fibers towards dyestuif is slight.

On the other hand, said fibers being hydrophobic and considerably morecrystalline than traditional fibers of polyvinyl chloride, it isdifficult to make the dye penetrate into the fibers, if the process isnot carried out under pressure.

The most satisfactory and practical method for dyeing these fibers isthat of incorporating the dye into the spinning solution before itsextrusion through the spinneret. This method presents, however, manydrawbacks, the main problem being constituted by the fact that a greatquantity of fibers of the same color must be prepared since, when achange of color is made, the entire spinning apparatus must first bethoroughly cleaned to remove all the traces of the dye used.

It has now been discovered, which discovery is the object of the presentinvention, that it is possible to dye in a continuous, rapid, uniformand deep manner, fibers or other shaped articles obtained via the wet ordry spinning of polyvinyl chloride with a high syndiotactic index, bymeans of a process comprising the following stages:

3,533,729 Patented Oct. 13, 1970 (a) dipping into a dyebath the fibersjust spun and which have not as yet been subjected to a dryingtreatment,

(b) suitably regulating the quantity of dyestuff on the fibers,

(c) subsequently subjecting the colored fibers to a thermal treatment athigh temperatures, and

(d) removing excess dyestutf by washing.

In fact, it was surprisingly found that, only by following at once theimpregnation of the fiber with a solution or dispersion of dyestutf witha thermal treatment at high temperature, was it possible to dyeuniformly and deeply polyvinyl chloride fibers having a highsyndiotactic index.

The treatment with a solution or dispersion of at least one dyestutf maybe carried out at any stage during the spinning process, but prior toany thermal drying treatment and in which the fibers are in suchcondition as to be abe to incorporate the dyestulf.

Therefore, for example, this treatment may be carried out during orafter coagulation of the fiber, or after the fiber has been coagulatedand washed or during or after stretching.

Furthermore, such a treatment may be carried out during the spinningcycle or subsequently, on condition that said fibers have not beensubjected to an intermediate thermal drying treatment.

Generally, best results are obtained when the fibers are stretched tothe ultimate value desired before being dipped into the dyebath.

However, in practice, it is also possible to partially stretch thefibers before dyeing; and in this case the subsequent stretching to theultimate value desired is carried out either during the thermaltreatment or after drying.

The dyebath may be advantageously composed of an aqueous solution ordispersion of at least one dyestutf, and even nonaqueous solutions ordispersions may be used.

The temperature of the dyebath is not critical with re gard to the shadeor the depth of the color which must be obtained.

Consequently, all temperatures ranging between room temperature and C.may be used.

At any rate, one of the advantages of the present invention is that itis possible to obtain a uniform, deep and rapid dyeing by operating atroom temperature.

However, in the case that the dyeing is effected during stretching, thetemperature, turns out to be higher, since the stretching is carried outat a temperature ranging from 90 and C.

The concentration of the dyestuff in the dyebath depends both on theparticular dyestuff used and on the shade and depth of the color whichmust be obtained.

Generally, such a concentration can vary from a very low concentration,0.001% by weight up to a saturated solution of dyestutf and also up tothe impregnation of the fiber with the dyestuff.

In practice, however, a better penetration of the dyestuff and auniformity of color are obtained by using relatively dilute solutions asdyebath.

During the dyeing, the concentration of the dyebath is kept constantlyat the desired value by adding, in a suitable way, a solution or adispersion of the dyestuff at a concentration such as to integrate thedyestufl removed by the fibers.

Generally, all water soluble and water dispersible dyestufls, includingpigments, may be employed advantageously. Specifically, among those thatmay be mentioned are vat, sulfur, direct, metallized, basic, acid,azoic, and plastosoluble, etc. dyes.

However, best results are attained by using plasto-soluble dyestuffs.

The time during which the fiber remains dipped in the dyebath is veryshort and such as not to slow down the spinning cycle. This time dependson the denier of the fibers and not on the number of the filamentscomposing the tow and generally it varies between some fractions of asecond and some seconds, and preferably between 1 to seconds.

In order to regulate the content of the dyestuif on the fibers accordingto the shade of the color to be obtained, according to the presentinvention, the fiber coming out of the dyebath are subjected towringing. The wringing of the fibers can be made in any suitable way.So, for example, the tow can be made to pass either through pressurerollers or through a narrow opening or on an acute angle under tensionetc.

Preferably, however, a pair of pressure rollers are used, where thepressure applied to the tow between the two rollers can be varied atwill.

According to the present method it is necessary and indispensable tofollow the treatment with a solution or dispersion of a dyestuff andsubsequent wringing of the fibers with a thermal treatment at hightemperatures in order to fix the structure of the fiber and, therefore,to firmly incorporate the dyestutf in the fibers.

Such a thermal treatment is carried out at a temperature comprisedbetween 100 C. and 220 C. and preferably between 130 C. and 170 C.

According to the process of the present invention, the fibers coloredafter the thermal treatment, are washed with hot water or aqueoussolutions of soap or of another detergent, preferably at boilingtemperatures, in order to remove excess dyestuff not included into thefibers.

The fibers thus obtained may be subjected to further additionaltreatments, such as finishing, lubrication, etc. before being dried inair or inert gas at a temperature comprised between 100 C. and 200 C.

The dyed fibers thus obtained exhibit excellent physical propertiesbesides the fact of being dyed in a deep and uniform way, both overtheir cross section and along their length.

With reference to the figure of drawing, a preferred method of thepresent invention will now be described. A bundle of filaments (tow) 1obtained by dry or wet spinning, according to known methods, of vinylchloride having a high syndiotactic index, at the outlet of thecoagulation bath or of the evaporation column is washed, at leastpartially stretched, passed around guide roller 2 and immersed into thedyebath 3 by means of guide roller 4 and 5. The dyed bundle of filaments6 is taken from the pressure rollers 7 regulating the quantity ofdyestuff on the fibers, thus eliminating excess dyestuff.

The dyed bundle of filaments is subsequently heat treated by making itpass around a series of hot rollers 8. The dyed and dried bundle offilaments thus obtained is thoroughly washed with boiling water whichmay also contain some detergent and which is subsequently subjected topossible further treatments commonly called finishing treatments, andfinally dried.

In order to further illustrate the present invention and the advantagesthereof, the following specific examples are given, it being understoodthat the same are merely intended to be illustrative and not limitative.

EXAMPLE 1 2 kg. of polyvinyl chloride, having a syndiotactic index of 2and an intrinsic viscosity (1;) of 1.3 dl./g., determined incyclohexanone at 25 C., were dissolved at 145 C. in 8 kg. ofcyclohexanone. The solution obtained was extruded through a spinneret of500 holes, every hole having 0.125 mm. diameter, into a coagulation bathcomposed of water, alcohol and cyclohexanone.

The tow thus obtained was collected by a pair of rollers having aperipheral speed of 7 m./min. The tow was then washed with boiling waterand stretched about 700% by a second pair of rollers having a peripheralspeed of 49 m./min.

The tow 1, by means of the rollers 2, 4 and 5, was dipped into thedyeing vat 3 containing an aqueous dispersion or solution of one of thehereinunder reported dyestuffs.

The tow was taken up and wrung by the pair of rollers 7 and thensubjected to a thermal treatment by making it pass around the rollers 8maintained at 150 C.

Subsequently and continuously, the tow was washed with boiling water,then finished and finally dried.

A tow was thus obtained, having a total count of 1,250 deniers, dyeduniformly and deeply, according to the shades peculiar to the followingdyestutf:

EXAMPLE 2 A tow of filaments of polyvinyl chloride with a highsyndiotactic index, obtained according to Example 1, at the outlet ofthe coagulation bath, was collected by a pair of rollers having aperipheral velocity of 7 m./min.

The tow was then washed with boiling water and stretched about 300% by asecond pair of rollers having a peripheral speed of 21 m./min.

The tow partially stretched, thus obtained, was dyed via dipping into adyebath containing any one of the dyestuffs reported in Example 1, thenit was thermally treated by passing the same over a series of rollersmaintained at 160 C.

The dyed tow, thus obtained, was washed with boiling water, finished,dried and then subjected, in a continuous way, to a successive stretchof 20% by means of a pair of rollers having a peripheral speed of 42m./rnin.

The tow, thus obtained, has a total count of 1,500 deniers andproperties similar to the tow obtained according'to Example 1.

EXAMPLE 3 A tow of 50 filaments, obtained by dry spinning a solution ofpolyvinyl chloride having a high syndiotactic index in cyclohexanone,was wound on reels. 10 of these reels were placed on a creel and unwoundat the speed of 10 m./min. by a pair of rollers, on which the 10 tow offilaments were gathered to form a single tow of 500 ends.

This last was washed and stretched about 500% by a second pair ofrollers rotating at a peripheral speed of 50 m./ min.

Subsequently, the tow was dyed by making it pass in a dyebath containingone of the dyestuffs reported in Example 1, then it was thermallytreated at 150 C., washed with boiling water and finally dried.

A tow was thus obtained, having a total count of 1,250 deniers, dyeduniformly and deeply.

As many apparently widely different embodiments of this invention can bemade without departing from the spirit and scope thereof, it is to beunderstood that the same is not to be limited to the specificembodiments thereof, except as claimed in the appended claims.

What is claimed is:

1. A process for rapidly, uniformly and deeply dyeing fibers obtained bywetor dry-spinning high syndiotactic vinyl chloride homopolymers,copolymers or mixtures of polymers containing at least by weight ofvinyl chloride, comprising dipping the said fibers into a dyebathcontaining at least one dyestuff, the clipping occuring subsequent tospinning but prior to any drying treatment of the said spun fibers,regulating the amount of dyestuff taken up by the said fibers,subjecting the thus colored fibers to a heat-treatment at a temperaturebetween and about 220 C., and thereafter removing excess dyestuif.

2. The process as defined by claim 1, wherein the fibers are at leastpartially stretched prior to their entry into the dyebath.

3. The process as defined by claim 1, wherein the fibers are stretchedto the ultimate value desired prior to their entry into the dyebath.

5 6 4. The process as defined by claim 1, wherein the References Citedelevated temperatures range from between 130 C. to UNITED STATES PATENTSabout 170 C. I

5. The process as defined by claim 4, wherein excess gfifiigg dyestufiis removed by Washing- 5 3 113 327 12 19 3 Moore, 7g 6. The process asdefined by claim 4, wherein the dye- 3,242,243 3/1966 Knudsen bathcomprises a member selected from the group consisting of an aqueousdispersion and an aqueous solution GEORGE F. LESMES, Primary Examiner ofthe Said dYcstuff' T J HERBERT JR AssistantE n r 7. The process asdefined by claim 6, wherein the con- 10 Xaml e centration of dyestulf inthe dyebath ranges from be- US. Cl. X.R.

tween 0.001 percent by weight and saturation level. 8-176; 26478

